The overall objective is to understand how tumor viruses, cell surface properties and growth factors affect cell growth regulation. There are three groups of projects. One is concerned with the molecular biology of tumor viruses and mechanisms of cell transformation. A second is concerned with cell surface immunology and biochemistry. The third is concerned with cell growth control by serum factors, hormones and nutrients. BIBLIOGRAPHIC REFERENCES: Rudland, P., Pearlstein, E., Kamely, D., Nutt, M., and Eckhart, W. Indepenent regulation of cellular properties in thermosensitive transformation mutants of mouse fibroblasts. Nature 256, 43-46 (1975). Eckhart, W., The 1975 Nobel Prize for Physiology or Medicine. Science 190, 650 (1975).